It is known in the past to use mine roof bolts to support the excavated earth strata in a mine. As shown in FIG. 1, one type of roof bolt consists of an elongated bolt which is held in the bore hole with resin. The end extending from the bore hole typically has a bearing plate secured with a nut. The nut is tightened to a recommended level to tension the bolt.
In a conventional installation, a bore hole is first drilled to the required depth. A resin cartridge is then inserted into the bore hole followed by the bolt. The bolt is then shoved to the top of the hole. The resin cartridge ruptures and fills the space between the bolt and the bore hole. To mix the resin, the bolt is typically turned a number of times. After mixing, the bolt is held snugly against the roof until the resin hardens. Once the resin hardens, the nut is tightened to tension the bolt.
A domed nut is typically used to ensure that the nut and bolt turn together during mixing of the resin. The domed nut has a breakaway top to allow the bolt to thread through the nut during the higher torque of tensioning.
However, there is a problem in that the domed nut necessary to provide the temporary stoppage is much more expensive than a conventional nut.
The present invention allows a conventional hex nut (or nut of any design--as square) to be used with the described mine roof bolt. A novel wrench and associated system is disclosed which provides the described dual function of turning the nut and bolt as one during resin mixing and turning the nut relative to the bolt during tightening.